Presently various fluids are used for heat transfer, cleaning solvents, deposition solvents and other purposes in the electronics industry. The suitability of a fluid depends upon the application process. For example, some electronic applications require fluids which are inert, have a high dielectric strength, have low toxicity, have good environmental properties, and have good heat transfer properties over a wide temperature range. Other applications require precise temperature control and thus the heat-transfer fluid is required to be a single phase over the entire process temperature range and the heat-transfer fluid properties are required to be predictable, i.e., the composition remains relatively constant so that the viscosity, boiling point, etc. can be predicted so that a precise temperature can be maintained and so that the equipment can be appropriately designed.
Perfluorocarbons, perfluoropolyethers, and some hydrofluoroethers have been used for heat transfer and other purposes in the electronic industry. Perfluorocarbons (PFCs) can have high dielectric strength and high resistivity. PFCs can be non-flammable and are generally mechanically compatible with materials of construction, exhibiting limited solvency. Additionally, PFCs generally exhibit low toxicity and good operator friendliness. PFCs can be manufactured in such a way as to yield a product that has a narrow molecular weight distribution. They can exhibit one important disadvantage, however, and that is a long atmospheric lifetime which can give rise to a high global warming potential (GWP).
Perfluoropolyethers (PFPEs) exhibit many of the same advantageous attributes described for PFCs. They also have the same major disadvantage, i.e., a long atmospheric lifetime which can give rise to a high global warming potential (GWP). In addition, the methods developed for manufacturing these materials can yield products that are not of consistent molecular weight and thus can be subject to performance variability.
Hydrofluoropolyethers (HFPEs), a class of hydrofluoroethers (HFEs), can exhibit some of the same advantageous attributes of PFCs, but differ greatly in two areas. They can exhibit markedly lower environmental persistence, yielding atmospheric lifetimes on the order of decades rather than millennia which can give rise to a lower, though still relatively high, global warming potential. However, some of the HFPEs taught as heat-transfer fluids can be a mixture of components of widely disparate molecular weight. Thus, their physical properties may change over time which makes it difficult to predict performance.